THE EFFECT ON MILK-PRODUCTION OF REPLACING GRASS-SILAGE WITH MAIZE SILAGE IN THE DIET OF DAIRY-COWS

This experiment examined the effects of replacing high digestibility g rass silage (GS) with maize silage (MS) grown under marginal climatic conditions on milk production and forage intake of Friesian cows. Fift y-six cows were fed 6 kg/d (fresh weight) of concentrates and one of f our forages: (1) all GS, (2) 67:33 GS:MS, (3) 33:67 GS:MS, and (4) all MS. Concentrate crude protein (CP) level was varied to equalise total dietary CP. The analysis of the GS and MS were: DM (g/kg) 223 and 257 , pH 3.91 and 3.98, and CP (g/kg DM) 155 and 91. The MS contained 219 g starch/kg DM. In vivo OM digestibilities were 0.782 and 0.674 (s.e.m . = 0.0063, P < 0.001) for the GS and MS respectively. Silage DM intak es were 8.8, 9.7, 10.4, and 10.7 (s.e.m. = 0.35) kg DM/d for treatment s 1 to 4, respectively. The intake on treatment 1 was significantly lo wer than on treatments 3 and 3 (P < 0.01 and P < 0.001, respectively). Milk yields were 21.4, 23.0, 23.1, and 22.7 (s.e.m. = 0.48) kg/d for treatment 1 to 4, respectively. The differences in milk yield between the GS only and the two GS:MS mixtures were significant (P < 0.05). Ma ximum milk protein concentration (31.6 g/kg) and yield of fat and prot ein (1.59 kg/d) were achieved on the mixed forage diet containing 67% maize silage. These results show that moderate quality maize silage ca n successfully replace a high proportion of high digestibility grass s ilage in dairy cow diets. (C) 1998 Elsevier Science B.V.